Cannabis

Key takeaways

  • Biological control agents (BCAs) released into propagation seed the canopy with beneficials before pest populations ever start — the most cost-effective stage to act.
  • Vegetative stage is when canopies bridge — predatory mites in slow-release sachets can spread plant-to-plant on their own.
  • In flowering, spray options shrink: pesticide residues persist in the final product and dense canopies block coverage. BCAs delivered through Universal Release Boxes (URBs) keep predators off developing flowers.
  • Top cannabis pests to plan for: hemp russet mite, broad mite, two-spotted spider mite, foliar aphid, and Western flower thrips.
  • For root-feeding aphids, the evidence supports approved mycoinsecticides at the root zone — not BCAs — despite common claims to the contrary.

Cannabis production demands a biocontrol program built stage-by-stage. The crop spends a long, intensive run from clone to harvest, and each stage — propagation, vegetative, flowering — rewrites which beneficials, release methods, and rates make sense. A plan built around the plant’s phenology beats any generic IPM template.

Tray of young cannabis clones rooted under propagation lights — early BCA release stage
Cannabis clones at the start of propagation — the most cost-effective stage to introduce biological control agents.

Clones & propagation

  • All incoming plant material should be dipped in a solution of horticultural or botanical oil, followed by a spray application three days later.
  • If incoming material is rooted, submerge the rooted area in an approved mycoinsecticide labelled for aphids, according to the label rate.
  • Reject or quarantine any incoming material with active infestations of pests or diseases.
  • Higher humidity in propagation can drive higher fungus gnat pressure — release biological control agents as soon as possible to prevent fungus gnat establishment.
  • Smaller areas and smaller plants mean lower release rates.
  • Releasing BCAs at this stage helps establish predators in the plants from the start of growth, so the canopy never goes uncovered.
Releasing BCAs in propagation establishes predators in the plants from the start of growth — the canopy is never uncovered.

Vegetative stage

Cannabis plants in the vegetative stage with bridging canopies under lights
Vegetative-stage cannabis — bridging canopies let predatory mites travel plant-to-plant on their own.
  • Canopy bridging begins in this stage, making releases easier as BCAs can travel from plant to plant on connected foliage.
  • Slow-release sachets of predatory mites are suggested at this point, as plants should be sturdy enough to support them.
  • Release rates increase as plants grow larger and foliage begins producing heavy leaf hairs and trichomes.
  • During this stage it is still optional to use approved and compatible pesticides.
  • “Over the top” applications of bulk predators remain a viable option.

Flowering stage

Cannabis flowering room with dense plant canopies and overhead lighting
Flowering room — dense canopies and developing flowers limit spray coverage and force BCA-driven IPM.
  • This is the most critical stage for pest pressure control. Spray options become limited because pesticide residues persist in the final product, dense canopies block spray coverage, and humidity spikes can drive mold or mildew (especially indoors).
  • “Over the top” applications are not recommended at this stage due to the risk of vermiculite or bran carrier sticking to the flower. Use Universal Release Boxes (URBs) to release predators within the canopy and avoid contact with developing flowers.
  • Larger plants, more leaf hairs, heavy trichome production, and zero tolerance for pest damage at this critical stage all push higher release rates.
In flowering, spray coverage collapses and residues persist. URB-delivered predators keep the canopy protected without touching the flower.

Cannabis pests & biological control agents (BCAs)

Hemp russet mite (Aculops cannabicola) & broad mite (Polyphagotarsonemus latus)

  • Due to microscopic size, early detection is critical for both hemp russet and broad mites.
  • “Vagrant” feeding on plant tissue causes varying symptoms often misdiagnosed as nutrient deficiencies.
  • Current management strategies are the same for both species.
  • Broad mite eggs have a distinctive dimpled, “jeweled” appearance — a target when scouting.
  • BCAs: Neoseiulus fallacis, N. californicus, Amblyseius andersoni, A. cucumeris.

Two-spotted spider mite (Tetranychus urticae)

  • Produces a complex webbing system used for plant-to-plant movement, egg-laying, and protection from predators or pesticides — the webbing must be removed before spray treatment to be effective.
  • The egg-to-adult life cycle shortens at higher temperatures, causing population explosions in outdoor and greenhouse crops in summer.
  • BCAs: Phytoseiulus persimilis, N. fallacis, N. californicus, Feltiella acarisuga, Chrysoperla rufilabris*.

Aphids — foliar and root-feeding

  • Despite common claims on the net or in cannabis publications, there is no scientific evidence supporting BCAs for root-feeding aphids. Approved mycoinsecticides labelled for aphids applied to the root zone are the best curative approach.
  • Foliar aphids can be controlled using parasitic wasps, predatory lacewing larvae, and predatory midge larvae.
  • BCAs: Aphidius colemani, A. ervi, C. rufilabris, Aphidoletes aphidimyza.

Western flower thrips (Frankliniella occidentalis)

  • Western flower thrips (WFT) is an overlooked pest in many cannabis grows — not as destructive to cannabis as to other crops, but it carries the potential to spread incurable plant viruses, causing significant crop losses.
  • WFT completes its pupal life stages below the soil/media surface, which means a mix of BCAs is needed to break the life cycle on both foliage and substrate.
  • BCAs: Orius insidiosus, A. cucumeris, Stratiolaelaps scimitus, Dalotia coriaria, Steinernema feltiae, C. rufilabris*.

* Suppression or enhancement to an existing program for the pest mentioned — not a standalone control agent.

Release rate guidance

Due to the varied growing styles and growing spaces of cannabis, release rates will vary based on many factors — stage of growth, level of infestation, time until harvest, and many more. High or low temperature and humidity can also shift which BCA is suggested for a specific situation. Consult an IPM specialist for release rates and BCA selection tailored to your facility.

For release rates for cannabis: please call 1.855.289.1441.

For over 30 years, Green Methods has been a leader in the production and application of beneficial organisms used in biological pest control and integrated pest management programs.

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